The present invention relates to an improved apparatus and method for the placement and flipchip bonding of a die on a substrate, and more particularly, to various aspects of an apparatus including, in different combinations, a movable die holder, a movable substrate holder, a pivoting transfer arm that picks a die from the movable die holder and transfers the die to a position adjacent the movable substrate lo holder, and a bondhead assembly for picking the die from the transfer arm and bonding the die to the substrate.
Hybrid circuit substrates including die or multiple dice bonded to a base circuit substrate are commonly used in many modern mechanical and electrical devices. During production of the substrate, accurate placement and time efficient bonding of the die on the circuit substrate is of considerable importance. These goals can be difficult to accomplish due to the small size of the die, which can be as small as 5xc3x975xc3x974 mils. Accordingly, there are numerous devices that attempt to accurately and efficiently position a die on a substrate for bonding, while taking into account the small size of the die.
Many of these prior art pick-and-place mechanisms hold the die, also called a chip, on a stationary die holder, also called a chip carrier, and attempt to pick the die from the holder with movable tweezers or similar devices. The tweezers typically are manually operated which results in operator fatigue and lack of uniform positioning of the die within the tweezers. This manual pickup method may also result in damage to the die, damage to the die holder, and a lengthy die pickup process. In another prior art device, the tweezers and the die are both moved into position before picking of the die occurs. This dual movement system includes many variables and often results in a mis-pick of the die. Once the die is picked from the holder by use of the tweezers, the die is moved into a placement or bonding position relative to the stationary circuit. This manual positioning step also subjects the operator to fatigue and may result in a lack of uniform placement of the die on the substrate. Once the die is positioned relative to the substrate, the die is bonded to the substrate by one of a variety of known methods. This bonding step often results in inaccurate bonding of the die to the substrate due to misalignment of the bond pads or bumps of the die with the corresponding bond pads or bumps of the substrate. Inaccurate bonding may also occur due to tilting of the die relative to the plane of the substrate. This inaccurate bonding of the die to the substrate may result in damage to the assembly or may result in an assembly that does not function as desired.
In the case of die pick-and-place mechanisms which attempt to maximize automated handling of the die, the precision machinery required may be quite expensive to purchase and upkeep, may require a large amount of space to store and operate (the machinery may require a space of 3 feetxc3x975 feetxc3x974 feet or even much more), may be heavy to install and support (the machinery may weight as much as half a ton or more) and may be slow in operation, especially when correction is required during the process due to the mis-pick or misplacement of a die. Moreover, these machines have problems associated with large machinery including planarity and tolerance errors.
Accordingly, there is a need for a mechanism and method for picking a die from a die holder, placing the die in a bonding position and bonding the die to a substrate, and that allows for time efficient and accurate positioning of the die while attempting to reduce the cost and size of the required machinery.
Accordingly, the present invention provides a die pick-and-place apparatus that facilitates complete automation of the die pick-and-place operations, allows for time efficient and accurate positioning of a die, provides a movable die holder for positioning a die in a predetermined die pickup position, and provides a movable substrate holder for positioning a bond site on a substrate in a predetermined die bonding position. The present invention also provides a die pick-and-place apparatus that is small in size and relatively inexpensive to manufacture, provides a transfer arm that picks a die from a predetermined pickup position and transfers the die to a predetermined die bonding position, and provides a bondhead assembly for bonding a die to a substrate wherein the bondhead assembly has few parts, has reduced friction within the assembly, and bonds the die to the substrate with high accuracy.
The preferred embodiments, in different combinations, include a movable die holder, a movable substrate holder, a pivoting transfer arm that picks a die from the movable die holder and transfers the die to a position adjacent the movable substrate holder, and a bondhead assembly for picking the die from the transfer arm and then bonding the die to the substrate. For purposes of the present invention, the term xe2x80x9csubstratexe2x80x9d can be defined as any chip receiving device such as a circuit, a package, a wafer, another chip, a standard substrate, or the like. Specifically, a preferred apparatus for practicing the various features of the invention includes a movable die holder that moves a die held on the die holder into a predetermined die pickup position for pickup by the transfer arm. The movable substrate holder moves the substrate so as that a bonding site on the substrate is aligned with a predetermined bonding position. The transfer arm pivots about a pivot axis between the predetermined pickup position and the predetermined bonding position which are each defined by the height of the transfer arm and the length of the transfer arm from its pivot axis. The bondhead assembly includes a bondhead that is aligned with the predetermined bonding position so that the bondhead receives the die from the transfer arm and then bonds the die to the substrate wherein the bondhead includes essentially frictionless flexure members.
One embodiment of the invention comprises an assembly for the placement and bonding of a die on a substrate, comprising: a carrier device that rotates about a rotational axis and including a die support position radially positioned about said rotational axis; an alignment device operable for manipulating in the x, y, z and rotational directions a die support held within said die support position so as to align a die held on said die support into a predetermined pickup position; a transfer arm having an elongate axis, a pivot axis positioned normal to said elongate axis, and a pickup surface, said transfer arm pivoting about said pivot axis to move said pickup surface from the pickup position to a placement position and said transfer arm rotating about said elongate axis so as to rotate said pickup surface approximately 180 degrees about said elongate axis during movement of said pickup surface from said pickup position to said placement position; a stationary heater block; a substrate gripping device positioned adjacent said heater block and moving in the x, y and rotational directions a substrate gripped within said substrate gripping device so as to align a bonding site on the substrate with a bonding position; and a bondhead assembly including a bondhead movable between a first position and a second position wherein said bondhead in the first position defines said placement position and said bondhead in the second position defines said bonding position.
In another embodiment the invention comprises an assembly for positioning a die for pickup by a transfer device, comprising: a carrier device that rotates about a rotational axis and including at least a first die support position and a second die support position each radially positioned about said rotational axis; a reader device aligned with said first die support position and operable for reading indicia placed on a die support held within said first die support position; an optical device aligned with said second die support position and operable for displaying an image of a die support held within said second die support position; and an alignment device aligned with said second die support position and operable for manipulating in the x, y, z and rotational directions a die support held within said second die support position so as to align a die held on said die support within said image displayed by said optical device.
In another embodiment the invention comprises an assembly for picking and transferring a die from a pickup position to a placement position for bonding on a substrate, comprising: a pickup station that defines a predetermined pickup position; a bonding station that defines a predetermined placement position; and a transfer arm having an elongate axis, a pivot axis positioned normal to said elongate axis, and a pickup surface, said transfer arm pivoting about said pivot axis to move said pickup surface from the pickup position to the placement position and said transfer arm rotating about said elongate axis so as to rotate said pickup surface approximately 180 degrees about said elongate axis during movement of said pickup surface from said pickup position to said placement position.
In another embodiment the invention comprises an assembly for positioning a die held on a die support into a pickup position, comprising: a carrier device for holding a die support therein; an optical device that displays an image of a die support held within said carrier device and that defines a predetermined pickup position; an alignment device that moves in the x, y, z and rotational directions a die support held within said carrier device; and a control device that receives directional input to control said alignment device to move said die support so as to move a die held on said die support into said predetermined pickup position. The directional input may be from a human operator or a computer controlled pattern recognition system.
In another embodiment the invention comprises an assembly for positioning a substrate into a bonding position, comprising: a substrate gripping device for gripping a substrate therein; an optical device operable to display an image of a substrate held within said substrate gripping device and operable to simultaneously display a predetermined bonding position; an alignment device that moves in the x, y and is rotational directions a substrate gripped with said substrate gripping device; and an operator control device that receives directional input from an operator to control said alignment device to move said substrate into said predetermined bonding position.
In another embodiment the invention comprises an assembly for bonding a die to a substrate, comprising: a stationary heater block; a bondhead assembly including a bondhead having an elongate axis, a flexure device, and a motor for moving said bondhead toward said heater block along said elongate axis and into a bonding position, said flexure device guiding movement of said bondhead along said elongate axis; and a substrate gripping device that moves in the x, y and rotational directions a substrate gripped within said substrate gripping device so as to align a bonding site on the substrate with said bonding position.
In another embodiment the invention comprises an assembly for aligning a substrate with a bonding position, comprising: a substrate gripping device that moves in the x, y and rotational directions a substrate held within said substrate gripping device so as to align a bond site on the substrate with a bonding position; a bondhead that defines a bonding surface for holding a die; a reflection device movable into an image capture position between a substrate held within said substrate gripping device and said bondhead; and a single optical device operable to display an image of a substrate held within said substrate gripping device and operable to display an image of a die held by said bondhead when said reflection device is moved into said image capture position wherein said image of the die defines the bonding position.
Another embodiment of the invention comprises an assembly for aligning a die with a die bond site, comprising: a substrate gripping device that moves in the x, y and rotational directions a substrate gripped within said substrate gripping device; a bondhead that defines a bonding surface for holding a die; an optical device that sequentially displays a real time image of a die held by said bondhead and a real time image of a substrate held within said substrate gripping device; and an image capture device that captures a template image of said die held by said bondhead and overlays said template image on the real time image of a substrate held within said substrate gripping device.
In another embodiment the invention comprises a method of aligning and bonding a die on a substrate, comprising the steps of: aligning a die with a predetermined die pickup position; picking the die from the predetermined die pickup position with a transfer assembly; transferring the die to a predetermined placement position with said transfer assembly; picking said die from the transfer assembly with a bondhead assembly; and bonding the die to a substrate with said bondhead assembly.